As the complexity of integrated circuits (IC) continue to increase the probability of a faulty component occurring in an IC approaches one, the faulty component may require that the IC be discarded. However, the use of redundant circuits, which are located on the IC alongside the normal circuitry of the IC, may permit the replacement of the circuitry containing faulty component. Therefore, the use of the IC may be salvaged. This can increase the IC yield and save the IC manufacturer a considerable amount of money. The redundant circuits can be activated and used in place of the faulty components (and the faulty component deactivated) by blowing fuses (such as electrical fuses (e-fuses) and/or laser-trimmed fuses). The use of fuses to activate redundant circuits and deactivate faulty components is a technique widely used in industry.
Components of an IC may be faulty due to several causes. A first cause may be that the component was not fabricated properly. For example, an imperfection may have been present on the substrate during fabrication or the fabrication procedure itself may be faulty. Improperly fabricated ICs may be discovered during IC testing, prior to packaging. If a faulty component is discovered on an IC during pre-packaging IC testing, the faulty component may be deactivated and a redundant circuit activated to take its place through the blowing of certain fuses, preferably, laser fuses since access to the IC is possible because the IC has yet to be packaged.
However, ICs may also be damaged after the pre-packaging IC testing. A second cause of faulty IC components may be that the component may have been damaged during the packaging of the IC. For example, when the die is cut from the wafer, when the wafer is cleaned, when the die is bonded to the packaging, and so forth. ICs that become faulty due to packaging are usually not discovered until post-packaging testing. Since the packaging of an IC can be a considerable amount of the overall cost of manufacturing the IC, simply discarding a faulty IC could be expensive.
A commonly used technique uses additional redundant circuits that can be activated in place of the faulty components discovered in post-packaging IC testing. These additional redundant circuits can be activated through the use of electrical fuses (e-fuses) rather than laser fuses since direct access to the IC is no longer possible. This can permit the use of a packaged IC that would have otherwise been discarded.
A disadvantage of the prior art is that the percentage of ICs that are damaged during packaging can be very small. However, to provide the ability to use those that are damaged, the redundant circuits need to be present in each IC. In order to minimize the complexity of the power and clock distribution system, the redundant circuitry usually shares a common power and clock distribution system with the remainder of the IC. This means that in the vast majority of ICs, the redundant circuitry is being actively clocked and powered although it is not being used. This can increase power consumption of the IC.